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Inclined Fire, part #3.5bis: 2I2R for victims of MOA

And now folks, a special edition of the 2I2R for unfortunate owners of scopes with clicks graduated in ¼MOA. (Many of my good friends fell victims of this perversion; US manufacturers of [otherwise excellent] scopes seem to love this.)

Improved Rifleman's rule:
1. Measure the inclination α;
2. Measure the slant distance (along LOS) D;
3. Look up bullet path (come-up) in ballistic table as if shooting at distance D horizontally;
4. Multiply this correction by cos(α).

The secret ingredient, 2I2R-MOA:
5. Subtract one click per each five degrees of inclination over twenty, i.e., 25º -1 click, 30º -2 clicks, 35º -3 clicks, etc.

Results for three different calibres, for the price of one -- check it out:

GP11 2I2R-MOA vertical miss distance, cm


15 20 25 30 35 40 45 50 55 60
300 1.1 2.0 0.9 0.0 -0.8 -1.4 -1.9 -2.0 -2.0 -1.7
400 1.4 2.7 1.3 0.0 -1.0 -1.6 -2.0 -2.2 -2.0 -1.3
500 1.6 3.1 1.3 -0.2 -1.4 -2.2 -2.7 -2.7 -2.3 -1.2
600 1.7 3.5 1.1 -0.6 -2.2 -3.2 -3.7 -3.6 -3.0 -1.5
700 1.5 3.6 0.8 -1.6 -3.3 -4.5 -5.1 -5.2 -4.3 -2.4
800 1.2 3.2 -0.1 -2.9 -5.0 -6.5 -7.3 -7.3 -6.4 -4.2
900 0.5 2.5 -1.5 -4.8 -7.4 -9.3 -10.4 -10.5 -9.5 -6.9
1000 -0.7 1.2 -3.7 -7.7 -10.9 -13.4 -14.8 -15.3 -14.2 -11.5












-15 -20 -25 -30 -35 -40 -45 -50 -55 -60
300 1.2 2.2 1.2 0.2 -0.5 -1.1 -1.5 -1.7 -1.6 -1.5
400 1.9 3.3 1.9 0.7 -0.1 -0.7 -1.0 -1.1 -0.9 -0.1
500 2.5 4.3 2.7 1.4 0.4 -0.1 -0.5 -0.5 0.2 1.2
600 3.2 5.6 3.8 2.4 1.2 0.6 0.4 0.6 1.5 3.1
700 4.2 7.1 5.1 3.6 2.5 1.9 1.8 2.3 3.4 5.6
800 5.5 8.9 6.9 5.4 4.3 3.9 3.9 4.7 6.2 8.6
900 7.1 11.2 9.2 7.7 6.8 6.5 6.8 7.9 9.6 12.7
1000 9.0 14.0 12.1 10.9 10.2 10.1 10.8 12.1 14.5 18.1

GP90 2I2R-MOA vertical miss distance, cm


15 20 25 30 35 40 45 50 55 60
300 1.1 2.1 1.0 0.1 -0.7 -1.3 -1.6 -1.8 -1.8 -1.6
400 1.6 2.9 1.6 0.4 -0.4 -1.0 -1.3 -1.3 -0.8 0.2
500 2.0 3.7 2.0 0.7 -0.3 -0.9 -1.0 -0.7 0.1 1.9
600 2.3 4.4 2.5 0.9 -0.1 -0.7 -0.8 -0.3 1.2 3.5
700 2.9 5.3 3.1 1.3 0.1 -0.4 -0.3 0.5 2.4 5.5
800 3.3 6.1 3.6 1.7 0.4 -0.1 0.0 1.2 3.5 7.5
900 3.2 6.1 3.1 0.8 -0.7 -1.4 -1.1 0.1 2.8 7.4
1000 1.3 4.0 0.0 -3.1 -5.3 -6.6 -6.7 -5.7 -2.9 2.2












-15 -20 -25 -30 -35 -40 -45 -50 -55 -60
300 1.3 2.2 1.2 0.2 -0.6 -1.2 -1.6 -1.8 -1.8 -1.6
400 1.7 3.1 1.8 0.7 -0.2 -0.7 -1.0 -1.0 -0.5 0.4
500 2.2 4.0 2.4 1.2 0.2 -0.3 -0.4 -0.2 0.7 2.3
600 2.8 4.9 3.1 1.6 0.6 0.1 0.0 0.6 1.9 4.1
700 3.3 5.9 3.8 2.1 1.0 0.4 0.4 1.1 2.9 5.7
800 3.7 6.7 4.2 2.4 1.1 0.6 0.7 1.6 3.7 7.1
900 4.9 8.5 6.0 4.2 3.0 2.6 3.0 4.3 6.8 11.0
1000 7.7 12.3 10.2 8.8 8.2 8.4 9.4 11.3 14.7 19.8

.338LM 2I2R-MOA vertical miss distance, cm


15 20 25 30 35 40 45 50 55 60
300 0.9 1.7 0.3 -0.9 -2.2 -3.3 -4.4 -5.6 -6.8 -8.4
400 1.2 2.2 0.5 -1.2 -2.7 -4.1 -5.5 -6.9 -8.3 -9.8
500 1.5 2.8 0.6 -1.5 -3.3 -5.0 -6.6 -8.2 -9.8 -11.5
600 1.7 3.2 0.7 -1.8 -4.0 -6.0 -7.9 -9.7 -11.5 -13.4
700 1.8 3.6 0.5 -2.3 -5.0 -7.2 -9.4 -11.5 -13.5 -15.5
800 2.0 4.0 0.4 -2.9 -5.9 -8.6 -11.0 -13.3 -15.3 -17.6
900 2.1 4.2 0.2 -3.6 -6.9 -9.9 -12.7 -15.3 -17.6 -19.9
1000 2.0 4.4 -0.2 -4.4 -8.1 -11.6 -14.5 -17.4 -20.0 -22.4












-15 -20 -25 -30 -35 -40 -45 -50 -55 -60
300 1.0 1.8 0.4 -0.8 -2.0 -3.2 -4.3 -5.4 -6.7 -8.2
400 1.4 2.5 0.7 -0.8 -2.4 -3.7 -5.1 -6.5 -7.8 -9.4
500 1.8 3.3 1.1 -0.8 -2.5 -4.1 -5.8 -7.2 -8.9 -10.7
600 2.3 4.2 1.6 -0.5 -2.6 -4.4 -6.2 -8.0 -9.7 -11.6
700 2.8 5.0 2.2 -0.4 -2.6 -4.7 -6.7 -8.7 -10.6 -12.5
800 3.5 6.0 2.8 0.0 -2.4 -4.8 -6.9 -9.1 -11.1 -13.2
900 4.3 7.1 3.7 0.6 -2.3 -4.8 -7.1 -9.4 -11.5 -13.9
1000 4.9 8.2 4.3 1.1 -2.0 -4.8 -7.2 -9.6 -12.0 -14.4

Is it not terrific?

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Article | by Dr. Radut